Traditionally, tricycles have been made with frames composed of various tubes welded together to provide the requisite supports for the usual seats, wheels and handlebars. A typical trike includes a downwardly-rearwardly curved tubular backbone which supports a seat. The upper forward end of the backbone is butt-welded to a vertical head tube and the tricycle's front fork rotatively supporting the front wheel is journaled in the head tube so that the fork can pivot about its vertical axis. Handlebars attached to the fork extend up from the tube so that a child sitting on the seat can maneuver the tricycle by turning the handlebars in one direction or the other. The lower rear end of the backbone is welded to structure for supporting the tricycle's rear wheels. That supporting structure is usually either an inverted U-shaped tube whose ends connect to the opposite ends of an axle carrying the rear wheels or to a horizontal step plate, with the rear axle being secured to that plate. In both constructions, the rear wheels are rotatively mounted to the opposite ends of that axle so that the tricycle seat is positioned above the ground in a horizontal plane.
It is apparent that the construction of a tricycle in this fashion requires several separate welding operations. More particularly, all of the tubular members comprising the frame, which are steel sheets or plates to begin with, must be formed and seam-welded into tubes. Also, separate welding steps are required to connect the opposite ends of the backbone to the head tube and to the rear supporting structure. In some tricycles, additional welding is required to add reinforcement at certain locations on the frame, e.g., at the location of the seat.
Usually, when a prior tricycle leaves the plant, its frame exists as a welded-together unit consisting of a backbone, head tube, rear step plate and rear axle. The remaining components of the tricycle, namely the rear wheels, the seat, the front fork with its wheel and the handlebar unit, are disassembled from the frame so that all of the tricycle parts can fit in a relatively small carton for shipment to the various points of sale throughout the country. The cost of shipping and warehousing the packaged product is proportional to the size of the shipping carton or package. That, in turn, is directly dependent upon the envelope occupied by the tricycle frame in the shipping carton since the frame is, by far, the least compact item in the carton. That is, the frame is an irregular structure that has considerable extent in all three dimensions. Obviously, the size of the tricycle shipping package cannot be reduced materially without reducing the spatial envelope occupied by the parts comprising that frame.
There have been some attempts in the past to alleviate this problem by forming the bicycle frame in sections for subsequent assembly by the purchaser. However, these attempts have not resulted in very marketable products because either the various parts are too costly to manufacture or they are difficult to assemble without special tools. And, in some cases, the assembled tricycle is not as strong and sturdy as might be desired.